signal

1n-countA signal is a gesture, sound, or action which is intended to give a particular message to the person who sees or hears it.They fired three distress signals..., As soon as it was dark, Mrs Evans gave the signal..., You mustn't fire without my signal.

2verbIf you signalto someone, you make a gesture or sound in order to send them a particular message.The United manager was to be seen frantically signalling to McClair...V prep/advHe stood up, signalling to the officer that he had finished with his client...V thatShe signalled a passing taxi and ordered him to take her to the rue Marengo.V n, Also V

3n-countIf an event or action is a signalof something, it suggests that this thing exists or is going to happen.with supp
(=sign)Kurdish leaders saw the visit as an important signal of support...

4verbIf someone or something signals an event, they suggest that the event is happening or likely to happen.
(=indicate)She will be signalling massive changes in energy policy...V nThe outcome of that meeting could signal whether there truly exists a political will to begin negotiating.V wh

5n-countA signal is a piece of equipment beside a railway, which indicates to train drivers whether they should stop the train or not.

6n-countA signal is a series of radio waves, light waves, or changes in electrical current which may carry information....high-frequency radio signals.

signal box(signal boxesplural)A signal box is a small building near a railway, which contains the switches used to control the signals.n-count

smoke signal(smoke signalsplural)If someone such as a politician or businessman sends out smoke signals, they give an indication of their views and intentions. This indication is often not clear and needs to be worked out.n-countusu plThe smoke signals from the central bank suggest further cuts are coming.

time signal(time signalsplural)The time signal is the series of high-pitched sounds that are broadcast at certain times on the radio, for example at exactly one o'clock or exactly six o'clock.(BRIT)n-countusu the N in sing

turn signal(turn signalsplural)A car's turn signals are the flashing lights that tell you it is going to turn left or right.(AM)n-countin BRIT, use indicators

Materialistic concept neonewtonist. In its measures, this variation of length of traveled route (by unit of time) by a group of photons ( φ is the initial of photons) - the light signal - is equal to what is collectively called " radial velocity". It distinguishes itself from it in its gnoseology.

Phys. Concept before 2007
The redshift indicates the phi-speed of a star. But do not give the immediate knowledge of its absolute speed.